| 摘要 |
1,232,219. Safety devices. L. SCHULER G.m.b.H. 1 Oct., 1968 [9 May, 1968], No. 46522/68. Heading F2J. A safety device ensuring stopping of a press ram in the event of a failure of the normal control system, the press being operated by a pneumatically controlled clutch and brake, comprises a valve 6 which, in the event of failure of the ram to stop in its top dead centre poistion, is actuated by a cam 44 on the main press shaft. Actuation of the valve 6 closes a passage between a port 3 leading to the clutch and brake and a port 2 connected to the compressed air supply by way of a main control valve (not shown) and opens the port 3 to a vent port 4 so that the clutch disengages and the brake is applied by spring pressure. The cam 44 cooperates with a follower roller 30 carried by a bell crank lever 29 pivoted to a lever 31 which is pivoted at 32 to the press frame. The lever 31 engages an end of the valve 6 and is engageable by a surface 33 of the lever 29. The lever 29 is pivotally connected to a single-acting piston 41 supplied with compressed air under the control of solenoid valve 43. On depressing a start button for single stroke operation of the press, the valve 43 is actuated so that compressed air acts on the piston 41 and shifts it to the right, thereby rocking the lever 29 and removing the roller 30 from the path of the cam 44 and also actuating a switch 26 which actuates contacts causing the main control valve to operate and thus supply pressure to start the press. Rotation of the cam 44 operates a switch 46 controlling the valve 43 so that the piston 41 is returned to its initial position by spring 23 and the roller 30 is brought into the path of the cam 44. At the end of a cycle, if the ram fails to stop in its top dead centre position (illustrated) the roller 30 will be displaced by a swell 45 on further rotation of the cam and levers 29, 31 will be rocked anti-clockwise and actuate the valve 6 to vent the clutch and brake so that the clutch disengages and the brake is applied. A pawl 34 has a step 36 holding the lever 31 in its displaced position and the pawl has to be reset manually before the press can be operated again. Actuation of the valve 6 also actuates a switch 16 which switches off the entire current supply to the press. |
